Long-Range High-Resolution Imaging With Silicon-on-Nothing ScAlN pMUTs

Abstract

This work demonstrates the imaging capabilities of a silicon-on-nothing (SON) ScAlN piezoelectric micromachined ultrasonic transducer (pMUT) array by a method of transmit beamforming followed by suitable signal postprocessing for 3-D image reconstruction. A 2.7-MHz pMUT array with 15% scandium-doped aluminum nitride (ScAlN) as the piezo thin film was implemented for this demonstration. A total of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$16\,\,{3} {}\times {}{3}$ </tex-math></inline-formula> -mm dies consisting of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${34} {}\times {}{37}$ </tex-math></inline-formula> pMUT elements per die and operated as dual channels were arranged in an eight-column <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> two-row array configuration, resulting in a 32-channel experimental system with a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$24\times6$ </tex-math></inline-formula> -mm coverage. In this work, experimental testing using single and multiple 6-mm-diameter reflectors at a different spacing from each other and a distance of 2.5 cm from the array was performed to validate the 3-D imaging capabilities of the developed 2-D SON ScAlN pMUT array with an attained lateral resolution of 5 mm.